WASHINGTON — President Obama withdrew his nomination of Caitlin Halligan to a federal appeals court Friday, handing a victory to Republicans in the Senate who twice blocked his pick for the key judicial post.

Calling the obstruction by Republicans unjustified and unacceptable, Obama said he agreed to Halligan’s request to be pulled from consideration even though she would have served with distinction on the US Court of Appeals for the District of Columbia Circuit.

‘‘I am deeply disappointed that even after nearly two and a half years, a minority of senators continued to block a simple up-or-down vote on her nomination,’’ Obama said in a statement the White House issued while he was traveling in Jordan.

Senate Republicans blocked Halligan’s confirmation for a second time in early March, arguing that Halligan is too liberal and citing her work on lawsuits against gun manufacturers and on behalf of illegal immigrants.

The Washington appeals court and its makeup are of critical importance to the president, with oversight of many of the actions his administration takes. The court handles challenges to most federal rulemaking and oversees federal agencies based in Washington.

It’s also something of a pipeline to the Supreme Court. Four of the nine Supreme Court justices served on the D.C. Circuit before being confirmed to the higher court.

Halligan was nominated to fill the position that John Roberts vacated when he became chief justice. There are four vacancies on the court, with judges nominated by Republican presidents holding a 4-3 majority.

Halligan’s nomination has been a flashpoint for Obama and Republicans since 2010, when Obama first tapped her and Republicans first intervened, using a procedural maneuver to prevent a vote on her confirmation. Obama renominated her at the start of 2013, but her confirmation again fell victim to GOP opposition in early March. Although a majority of senators, 51, supported Halligan’s nomination, Democrats needed 60 votes in the 100-member Senate to get it past Republican objections.

5 sites selected to become national monuments

WASHINGTON — President Obama is designating five new national monuments, using executive authority to protect historic or ecologically significant sites —including one in Delaware sought by Vice President Joe Biden.

The White House said Obama would make the designations Monday, using the century-old Antiquities Act to protect unique natural and historic landmarks. The sites are Río Grande del Norte National Monument in New Mexico; First State National Monument in Delaware; Harriet Tubman Underground Railroad National Monument in Maryland; Charles Young Buffalo Soldiers National Monument in Ohio; and San Juan Islands National Monument in Washington state.

The Delaware monument, commemorating the state’s history and preserving about 1,100 acres near Wilmington, is the first step toward creating a national park in Delaware, the only state not included in the national park system. The project is a longtime priority for Biden, a former senator from Delaware.

‘‘This national monument will tell the story of the essential role my state played in the history of the United States. I couldn’t be more proud to call Delaware home,’’ Biden said in a statement.

The largest site is Río Grande del Norte in New Mexico, where Obama will designate nearly 240,000 acres for protection. The site includes wildlife habitat valued by hunters and anglers; rafting, camping, and other recreation; and is prized by the region’s Hispanic and tribal groups.

The San Juan Islands monument off Washington’s northwest coast includes roughly 1,000 acres of public land already managed by the Bureau of Land Management. Supporters say the designation will protect important cultural and historical areas and safeguard natural areas used for recreation and other purposes.

The Arlington, Va.-based Conservation Fund donated property on Maryland’s Eastern Shore to the National Park Service to help tell the story of Tubman and the underground railroad. Tubman escaped slavery at age 27 but returned to Maryland’s Dorchester and Caroline counties to help slaves escape to the North.

The Charles Young monument in Xenia, Ohio, recognizes and celebrates Colonel Charles Young, a West Point graduate who was the first black national park superintendent. Young was the highest-ranking black officer in the Army until his death in 1922.

The new monuments would be the first designated by Obama in his second term. Obama created four national monuments in his first term.